Yupp! It's classified as a safe excercise during pregnancy (: along with walking and swimming! (:
It is fine when you are not far along I would say but I wouldn't try riding while 8 months pregnant!
I'm 29 weeks and ride bike all the time. I was told it was safe as well and I enjoy it!
I was told not to after 12 weeks by my Dr for the chance of falling since we have less center of balance